21991104 has 84 divisors (see below), whose sum is σ = 64019176. Its totient is φ = 7216128.

The previous prime is 21991091. The next prime is 21991117. The reversal of 21991104 is 40119912.

It is an interprime number because it is at equal distance from previous prime (21991091) and next prime (21991117).

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 41787 + ... + 42309.

Almost surely, 2^21991104 is an apocalyptic number.

21991104 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21991104, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32009588).

21991104 is an abundant number, since it is smaller than the sum of its proper divisors (42028072).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21991104 is a wasteful number, since it uses less digits than its factorization.

21991104 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 614 (or 601 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 27.

The square root of 21991104 is about 4689.4673471515. The cubic root of 21991104 is about 280.1661598799.

The spelling of 21991104 in words is "twenty-one million, nine hundred ninety-one thousand, one hundred four".